Piston ring and assembly therefor



Aug. 2, 1%. B. c. BRHSTOW PISTON RING AND ASSEMBLY THEREFOR Filed NOV. 1, 1933 fol/v mVENToR flarnard Cir/5 run/2 ATTORNEYS Patented Aug. 25, 19 6 UNITE STATES PATENT OFFICE PISTON RING AND ASSEMBLY 'rnnanroa Barnard 0. Bristow, San Francisco, Calif. Application November 1, 1933, Serial No. 696,194 2 Claims. (01. 309-24) This invention relates generally to piston assemblies such as are utilized in internal combustion engines, compressors and the like, and to piston rings and other individual parts which enter into such assemblies.

' It is an object of the invention to provide an assembly of the above character which will afford more adequate provision against leakage about the piston ring and ringlands, and which can be utilized both for the rehabilitation of worn assemblies and for incorporation in the structures at the time of initial manufacture.

A further object of the invention is to provide a piston assembly of the type utilizing a dished l5 resilient segment positioned at one end of the piston ring, which will avoid detrimental engagement between the outer edge, of the segment and the adjacent cylinder walls.

Another object of the invention is'to provide a novel type of dished resilient segment for use in conjunction with piston assemblies, which can be readily manufactured to accurate dimensions and which can be readily incorporated with a piston ring to afford more adequate sealing.

A further object of the invention is to provide an assembly of the above character which will more adequately compensate for wear of the ringland surfaces, which will tend to minimize pounding ofthe ring in the, event the ringlands have become worn, and which will tend to straighten badly worn ringlands in which rings of standard construction can not be properly fitted.

Further objects of the invention will appear from the following description in which the 'preferred embodiment of my invention has been'set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a cross-sectional detail on an enlarged scale, showing a piston assembly incorporating the present invention.

1 Figure 2 is a side-elevational view, partly in cross-section, illustrating a piston ring formed in accordance withthe present invention.

Figure 3 is a side-elevational view, partly in cross-section, illustrating a resilient segment such as is utilized in the present invention.

Figure 4 is a plan view of the segment illustrated in Figure 3. Figure 5 is an enlarged cross-sectional detail taken along the lines 5-5-of Figure 4.

Figure 6 is an enlarged cross-sectional detail similar to Figure 1, showing an assembly incorporating the present'invention for the purpose of 66 sealing against oilleakage.

. ringlands by impact.

Figure '7 is an enlarged cross-sectional detail similar to Figure 1, showing anassembly for a. compression ring having both upper and lower seals, to tend to render the ring free floating.

Fig. 8 isan enlarged cross-sectional view of a 5 modification embodying a dished ring disposed in a recess between the inner and outer faces of a compression ring.

My invention is intended to be used with pistons of standard construction, such as are utilized 10 in internal combustion engines, steam engines, compressors, and like appliances. In the past, piston assemblies for such appliances have generally made use of pistons provided with a p1u-, rality of annular grooves, fitted with splitmetal 15 piston rings which expand upon the side walls of the cylinder to form a sealing engagement. Ininternal combustion engine practice, and likewise in certain compressors, at least one of these rings is designed primarily to avoid undesired leakage or 20 pumping of oil, rather than primarily for the purpose of withstanding pressure. The effectiveness of'such a piston ring to afford adequate sealing depends not only upon securing proper contact between the outer peripheral surface of the ring 25 and the adjacent cylinder walls, but also upon the engagement between the side faces of the ring and the adjacent opposed surfaces or ringlands of the associated piston groove. Itis not difficult to afford proper sealing contact between the 30 outer peripheral surface of the ring and the adjacent cylinder walls, but sealing against leakage around the piston rings-that is,, between the side faces of the rings and the adjacent ringlandsis recognized as being diflicuit. In prac- 5 tice the side faces of the rings are ground and the ringlands of the piston are machined, but,

due to inaccuracy and metal warpage, a perfect seal is not provided. During a "breaking in period of use, the ring sides form a seat upon the 40 Such a seat does not form a perfect seaL however, and further pounding during use causes continued wear with resultant increased leakage. To properly repair such a worn assemblyis somewhat diflicult and gener- 45 1 ally necessitates the use. of oversized piston rings which must be fitted with respect to remachined ringlands.

It has bee'nproposed, particularly for the purpose of repairing worn piston assemblies, to insert 50 one or more thin metal segments between one side face of the piston ring and the adjacent ringland. These segments are made to a diameter. substantially larger than that of the cylinder,-so that when installed they are contracted with their outer edges bearing upon the cylinder walls. They are also formed with a certain amount of dishing, so that when contracted in a piston assembly the amount of dishing is increased somewhat to exert a thrust upon the associated ring. Contraction increases the radial pressure and the side pressure in relation to the increased dishing caused by contraction. If great care and precision are not exercised, the segment will press too heavily upon the cylinder-walls and mutilation will result, or, if not stressed to a suflicient degree, proper sealing will not be afforded.

As has been indicated by the aforesaid objects of the invention, in the assembly disclosed herein segments are provided which can be readily manufactured to accurate dimensions, and these segments co-operate with the piston rings in such a manner that detrimental engagement of the outer edges of the segments with the cylinder walls is avoided. Likewise, in my'invention the segments are not stressed by contracting the same, but they actually retain substantially their original diameter when incorporated in. the assembly.

Referring now to the drawing, in Figure 2 there is shown a piston ring II), which is formed split as in present day practice. One side face of this ring is formed to provide an annular recess I2 which serves to afford an outer annular shoulder The resilient segment which I prefer to employ with the ring of Figure 2 has been illustrated in Figures 3 to 5 inclusive. This segment,- indicated generally at I4, is formed of relatively thin, fiat spring metal, it is circular in contour with respect to its inner and outer edges, and it is dished to a substantial degree. The amount of dishing of course depends upon the'nature of the assembly in which the segment is to be employed, but in practice I have found that a dishing of about 15 gives good results. It will be noticed that the outer diameter of this segment is considerably smaller than the internal diameter of the shoulder I3 on ring ID. The significance of this proportioning will presently be explained in detail. However, at present it may be noted that the outer diameter of the segment conforms substantially to the inner diameter of the shoulder I3, when the ring In is contracted within a cylinder.

Figure 1 shows a piston ring and a segment as described above, assembled in the groove of a piston, as in an internal combustion engine. I Wall I G in this instance represents a portion of the piston; groove I1 is one of-the circumferential grooves in which a piston ring is disposed; and wall I8 represents a portion of the cylinder. The upper and lower opposed faces I9 and 2I of the groove II are the ringlands between which the piston ring I0 is fitted. Segment I4 is shown disposed within the recess I2, with its concave face disposed upwardly. In forming this assembly the segment I must of course be sprung over the piston to position it within the groove I1, and the piston ring must likewise be sprung into this groove with the recess l2 accommodating the segment, after which the ring is contracted and the assembly placed within the cylinder. In this assembly the diameter of the inner face 22 of shoulder I3 is in conformance with the outer di ameter of the segment I4 at the time of manufacturing the same. However, the segment is sprung in a lateral direction, and because of its sprimg condition it tends to press outwardly upon shoulder I3 to press the ring III more tightly against the cylinder walls. The amount of this outward radial pressure upon the piston ring is preferably such as to substantially compensate for weakening of the ring due to the formation of recess I2. The springing of the segment I4 within its elastic limit likewise tends to continuously force the piston ring upwardly against the ringland I9, to afford a more adequate seal at this point. Now, assuming that. pressure occurs downwardly from a chamber above the piston, contact between the outer peripheral surfaces of the piston ring III and the side walls of the cylinder affords an effective seal. Contact between the upper side surface of the piston ring and the ringland I9 tends to minimize leakage of pressure to the space bebind the piston ring. However, gas pressure leakage behind the piston ring is effectively prevented from seeping below the ring by virtue of the segment I4. The points at which the segment I eifects sealing have been indicated by the arrows I, 2 and 3. Point I represents a narrow annular area of contact (substantially a line contact) between the outer face of the segment I4 and the ringland 2I, along the inner edge of the segment. Point 2 represents a narrow annular area of contact between the inner face of the segment [4 and the bottom surface of recess I2, at the outer edge of the segment. Point 3 represents engagement of a narrow annular area between the. outer edge of the segment and the inner face 22 of the shoulder I3. These areas of contact are relatively continuous about the assembly because of the stressing to which the segment is subject and because the seg'ment is accurately formed in the first instance. It will also be noted that pressure existing behind the piston ring tends to press downwardly upon the segment I4 to secure an even more forcible sealing contact at the points I and 3.

It is of course to be understood that Figure 1 has been exaggerated with respect to the proportioning of the parts and with respect to the clearances afforded. Ordinarily, the clearances will of course depend upon the tolerances used during manufacture and upon the amount of wear to which the parts have been subjected. In the event considerable clearance may exist between the ends of the piston ring and the ringlands I9 and 2 I, it is evident that the stressing of segment I4 will tend to efi'ect an adequate seal in spite of such clearances, and movements of the ring with respect to the piston will be cushioned to minimize pounding. Likewise, slight downward movement of the ring with respect to the associated piston will tend to stress the segment to an even greater amount than normal to force the points of sealing contact more effectively into engagement. When the assembly is in use, slight movement of the ring with respect to the piston causes sliding movement between segment I4 and the ringland 2|. so that the point of sealage I is seated more effectively by rubbing action, as distinguished from pounding or impact.

Aside from the features which have been pointed out above, the position of the shoulder I I, engaged with the outer edge of the segment I 4, prevents direct contact between the outer edge of the segment and the cylinder walls. Likewise, engagement between the outer edge of the'segment and the inner face 22 of the shoulder l3 affords an added area of sealing engagement, as

has been previously explained.

Figure 6 represents a. modified piston assembly, for the purpose of preventing too great a flow of oil upwardly between the piston and the cylinder walls; and to prevent oil pumping. Thus, in this case the ring In is shown inverted, with its recess uppermost. Segment I4 is also applied upon the upper face of the ring, with its concave face downwardly. The segment affords three points of sealing engagement with the ringland l9 and the ring It, substantially as has been described with respect to Figure 1. Therefore, any oil finding its way behind the ring I0 is prevented from passing upwardly beyond the ring, due to the seal thus afforded. If desired, the groove I! in this instance may be in communication with the crankcase of the engine or compressor with which the assembly is employed, by way of ducts 26.

In Figure 7 there is shown a further modified form of assembly, in which segments are provided at both the upper and lower sides of a compression ring. In this case, in addition to providing the annular recess H2 at the lower side of the ring iOa, the opposite side of the ring is provided with another annular recess 21?. Recess i2 accommodates segment M, as in Figure 1, and the upper recess 21 accommodates a similar segment Ma. Both the segments I4 and a are stressed laterally so that they press in opposite directions upon the ring and likewise tend to expand the ring against the cylinder walls. Points of sealing engagement 8, 2 and 3 are afforded by the segment I4, and segment Ma also provides points of sealing engagement 5, t and I. It is apparent that in such an assembly the upper segment Ma will largely seal the ring against leakage of pressure behind the piston ring, whilel pressure leaking to a point behind the piston ring is further sealed against leakage beneath the ring, by the lower segment Hi. Therefore, such a ring will tend to be free floating, it will not be pressed with undue force against the sides of the cylinder walls by virtue of pressure behind the same, and it will not tend to be pressed into tight gripping engagement with the ringlands during operation of the engine or compressor in which the assembly is employed. A minimum of friction therefore results, in addition to sealing against leakage of pressure.

A further modification of the invention is shown in Fig. 8. In this instance the piston ring I 6b has one of its side faces provided with an annular recess 28, having both outer and inner annular shoulders 29 and 3|. A dished segment 32, similar to segment I4 exceptas to dimensions, is positioned within recess 28, and this segment has forcible sealing contact with the bottom face of the recess and the adjacent ringland 33, as indicated byarrows I and 8 respectively. If desired segment 32 may be proportioned so ,as not to have sealing contact with the inner face of shoulder 29, since ample sealing is afforded at points 1 and 8. i

It is evident that my invention is of particular value in repairing or rehabilitating worn piston assemblies. Increased tolerances due to wear can be compensated for, and much work in fitting in new rings can be obviated. My assembly can even be usedtsuccessfully in rehabilitating assemblies where the ringlands have been worn to a degree where they are non-parallel, since the sealing engagement is confined to a substantially line contact near the bottom of the piston groove. In fact, a worn assembly rehabilitated by -my invention actually has a tendency to can be made by a punching operation which simultaneousiy applies the desired dish, after which they can be accurately ground to the desired inner and outer diameters.

I claim:

1. In an assembly of thecharacter described, a piston ring fitted within an associated piston groove, said ring having an annular recess formed in one of its side faces whereby an annular outer shoulder is provided, and the'inner peripheral surface of said shoulder being substantially cylindrical, and a dished annular shaped segment of resilient material positioned within said recess and stressed laterally within its elastic limit, one face of said segment adjacent the inner edge of thesame having substantially uninterrupted annular sealing engagement with the adjacent ringland surface, the other face of the segment adjacent the outer edge of the same having substantially uninterrupted annular sealing engagement'with the bottom surface of the recess, and the outer periphery of the segment having substantially uninterrupted annular contact with the inner peripheral surface of said shoulder.

2. In an assembly of the character described, a piston ring fitted within an associated piston groove, said ring having an annular recess formed in one of its side faces whereby an annular outer shoulder is provided, the inner peripheral surface of said shoulder being substantially cylindrical and the bottom of the recess which forms the adjacent annular side of the ring being substantially planar, and a relatively thin dished annular segment of resilient material positioned within said recess and stressed laterally within its elastic limit, one face of said segment adjacent the outer edge of the same having substantially uninterrupted annular sealing contact with the adjacent ringland surface, the other face of the segment adjacent the outer edge of the same having substantially uninterrupted annular sealing engagement with the bottom surface of the recess, and the outer periphery of the segment having substantially uninterrupted annular contact with the inner face'of said shoulder, the

outer diameter of the segment being substantially the same as when unstressed apart from the assembly:

BARNARD C. BRISTOW. 

